The present disclosure relates to a power conversion apparatus, and more particularly, to a power conversion apparatus having a boost power factor correction (PFC) function and controlling inrush current and a power conversion method thereof.
A power conversion apparatus has a boost PFC function for power factor compensation. Herein, the power factor is represented by a ratio of active power to apparent power, i.e., a ratio of power actually flowing to a load to the apparent power.
In the power conversion apparatus having the boost PFC function, inrush current for charging a capacitor on a boost PFC output terminal at the initial time needs to be controlled.
That is, to protect a circuit when power is initially supplied thereto and to optimally design the circuit, the inrush current needs to be controlled.
FIG. 1 is a diagram illustrating power conversion apparatuses according to the related art.
Referring to FIG. 1(A), a power conversion apparatus includes a thermistor 10 for controlling initial inrush current.
The thermistor 10 has a high resistance when temperature is low, but has a low resistance when it is self heated or external temperature increases.
By using these characteristics, the initial inrush current is limited due to the relatively high resistance of the thermistor 10 when power is initially supplied, and when temperature become high, the initial inrush current is limited as the decreased resistance of the thermistor 10 causes construction of a closed circuit.
Although the power conversion apparatus using the thermistor 10 is simple, as illustrated in FIG. 1(A), the power conversion apparatus may not be applied to a high-capacity device as the thermistor 10 is not suitable for the high-capacity device.
Furthermore, efficiency of the power conversion apparatus using the thermistor 10 is degraded due to a loss caused by the resistance of the thermistor 10. Moreover, when the power conversion apparatus is abnormally operated, the temperature of the thermistor 10 may not decrease. In this state, a circuit cannot be separated from a grid, and thus cannot be protected before a fuse is opened.
Referring to FIG. 1(B), a power conversion apparatus includes a resistor 20 and a relay 30 for controlling the initial inrush current.
The power conversion apparatus charges a capacitor CB by using the resistor 20, and short circuits the relay 30 when the charging of the capacitor CB is completed so that current flows through the relay 30 instead of the resistor 20, thereby controlling the initial inrush current.
Although the power conversion apparatus using the resistor 20 and relay 30 illustrated in FIG. 1(B) is suitable for the high-capacity device, the power conversion apparatus has a limited life as the relay 30 forms a mechanical contact point.
Furthermore, when the separation from the grid is needed due to abnormal operations, it is difficult to rapidly perform the separation due to a slow response speed of the relay 30.
Moreover, even though the relay 30 is separated, the complete separation from the grid is difficult as current still flows through the resistor 20. Therefore, a relay circuit needs to be additionally connected in series to the resistor, thereby increasing a cost and a volume of a system.